A ground lift dump function within an aircraft flight control system is known. This function generally involves the control of the movement of some or all of the plurality of “spoiler” flight control surfaces located on the top surfaces of the wings of an aircraft during certain phases of aircraft flight. The movement typically involves some or all of the spoilers being fully extended or deployed into a position within the airflow passing over the aircraft wings. The deployed spoilers significantly reduce the lift of the wing section located aft of the spoilers (as well as increasing or augmenting the drag on the wings of the aircraft). This generally occurs when the aircraft is on the ground after being in-flight or is on the ground during an aircraft takeoff condition that has been rejected and the pilot must stop the plane before ever taking off. In either critical flight phase, the deployment of the spoilers slows the aircraft, thereby assisting with the braking of the aircraft. More particularly, the ground lift dump function helps to keep the wheels of the landing gear in contact with the ground, thereby improving the braking efficiency of the aircraft. The ground lift dump function thus helps the pilot to achieve a more controlled stopping of the aircraft.
Modern aircraft typically have a pair of ground spoilers (one on the top surface of each wing) that may be located “inboard” (i.e., relatively close to the aircraft fuselage) on each wing. These ground spoilers usually function only to assist with the stopping of the aircraft. As such, they generally have only two positions: fully retracted during normal in-flight aircraft operation, and fully extended or deployed while the plane is on the ground to assist with stopping the aircraft.
These modern aircraft may also have one or more multi-function spoilers located on the top surface of each wing, for example, at the mid-span point or more outboard on the wing. These spoilers may also be used similar to the ground spoilers to help stop the aircraft while it is on the ground after aircraft flight or after a rejected takeoff. As such, each multi-function spoiler is commanded to its fully extended or deployed position, similar to the ground spoilers. This may also allow the pilot to start placing a drag condition on the aircraft while the aircraft is still in-flight and prior to landing.
However, in contrast to the ground spoilers which have only two operating positions (e.g., fully retracted and fully deployed), the multi-function spoilers are also operable at a multitude of “controlled angle” positions in between the fully extended and deployed positions. This allows the multi-function spoilers to assist the pilot with the control of the roll of the aircraft. When used to control the aircraft roll, the multi-function spoilers may be deployed asymmetrically. The aircraft roll control using the multi-function spoilers may be accomplished either manually by the pilot or co-pilot or automatically by the aircraft flight control system when the autopilot is engaged.
Typically, the multi-function spoilers are manually commanded to move by the pilot or co-pilot using a control lever located in a center console of the cockpit or by the pilot or co-pilot using his/her sidestick or yoke controller. Usually, the position of each multifunction spoiler is proportional to the manual command given by the pilots. Also, in the ground lift dump function typically the ground spoilers both move in tandem when commanded and all of the multi-function spoilers move together in the same amount. In the ground lift dump function, it is generally desirable to avoid an “asymmetric” spoiler deployment condition in which one of the spoilers on one wing is deployed but the opposing or “mating” spoiler on the other wing does not deploy. This could cause a dangerous condition for the aircraft.
Thus, the ground lift dump function within an aircraft flight control, whether a modern “fly-by-wire” type of flight control system or a more traditional mechanical or hydro-mechanical type of flight control system, must function during critical phases of flight. As such, the ground lift dump function ideally should be designed to meet relatively tight safety requirements.
It is known that the ground lift function within an aircraft flight control system is typically armed for activation prior to deployment of the spoilers. The arming is usually performed by the pilot or co-pilot, and it is known to be carried out manually, for example, by one of the pilots activating a button or a lever at a certain point in time during aircraft flight (e.g., just prior to landing). Conversely, the ground lift function is typically disarmed during other flight phases (e.g., the taxi or parking phases). This type of manual arming increases the workload of the pilots and, as such, may lead to procedural errors. For example, if the pilot fails to properly arm the ground lift function at a particular time, there could be a risk that the deployment of the spoilers may not occur in time or may not occur at all. This could lead to dangerous and even catastrophic effects for the aircraft.
What is needed is an improved ground lift dump function within an aircraft flight control system in which the arming of the function is performed automatically, thereby eliminating the risks associated with the manual arming of the ground lift dump function by the pilots mentioned hereinabove.